1. Field
One embodiment of the present invention relates to a method of manufacturing a magnetic recording medium, such as a patterned medium.
2. Description of the Related Art
In recent years, the problem that improvement in track density is disturbed by interference between adjacent tracks has arisen with respect to a magnetic recording medium mounted on a hard disk drive (HDD). In particular, it is an important technical subject to reduce the fringe effect of a write head field.
As measures against this problem, a discrete track recording (DTR) medium has been developed, which is configured to physically separate recording tracks by processing a ferromagnetic layer. With the DTR medium, it is feasible to reduce side erase (erasure of adjacent track information when writing) and side read (reading of adjacent track information when reading), so that track density can be increased. Therefore, the DTR medium is expected to be a magnetic recording medium capable of providing high recording density. Also, a bit-patterned medium (BPM), which has dotted magnetic patterns, is expected to be a magnetic recording medium capable of providing a high recording density.
As a process for manufacturing the patterned medium (DTR medium, BPM), the following method is known. The known method comprises forming a hard mask and a resist on a magnetic recording layer, transferring patterns of protrusions and recesses to the resist by an imprint technique, transferring the patterns of protrusions and recesses of the resist to the hard mask and etching the magnetic recording layer using the hard mask as an etching mask to thereby form the magnetic recording layer with the patterns of protrusions and recesses.
A technology employing two hard mask layers is disclosed as an example of the above method in Jpn. Pat. Appln. KOKAI Publication Nos. 2005-50468 and 2006-12332. In the references, the technology relating to the step of removing any imprint residue of the resist, transferring patterns to the hard mask lying immediately beneath the resist and transferring patterns to the lowermost hard mask layer are disclosed, which are carried out using different etching gases. In the disclosed technology, when the etching selectivity between the resist and the hard mask lying immediately beneath the resist is very high (for example, 10 or higher), desirable processing can be performed. In contrast, when the selectivity is not sufficient, the resist mask is further etched during etching the hard mask lying immediately beneath the resist, so that an undesirably small pattern width results. Consequently, a low land/groove ratio (namely, a ratio of protruded pattern width to recessed pattern width) results. Therefore, the problem that satisfactory signal quality cannot be obtained in write and read with a head after mounting the medium on a drive arises.